電路板上PBGA元件之振動疲勞壽命試驗與可靠度分析

The Vibration Fatigue Life Test and Reliability Analyses for PBGA Components on PWB

楊裕州(Yu-Chou Yang)

指導教授 ： 陳 永 樹

元智大學/工程學院/機械工程學系/碩士(2003年)

摘要

電子裝置在受到振動一段時間後，由於元件的共振往往會造成材料的疲勞損壞導致元件失效，所以振動時實際元件壽命可以有多久？是一個耐人尋味的問題。在本研究中藉由組件的共振頻率，經由實驗、有限元素分析與理論的相互配合，探討實驗測試之元件失效與元件或系統壽命之關連性。
實驗部分為將銲接於電路板上具有Daisy Chain 之PBGA元件，以涵蓋其振頻之週期性振波做振動測試，直到元件失效為止，以探討PBGA在銲錫接合處的的可靠度。由於銲錫接合處的應力值不易直接由實驗所獲得，所以利用有限元素分析之方法，來模擬真實受力情況下錫球接合處之應力大小，再與實驗所獲得的疲勞循環數相互配合對照。使用曲線嵌合的方法配合理論中疲勞壽命公式，求得應力與疲勞壽命循環數的對照圖，接著作Weibull可靠度分析，以及Miner模式計算壽命。
研究的結果發現，錫球的疲勞破壞位置在錫球與電路板的接合界面上，實驗所得的應力-疲勞壽命結果與相關文獻中所述之破壞位置與實驗結果頗為吻合。綜合言之，本研究對於電子系統之壽命分析，提供一個有效之可靠度驗證模式。雖然各系統或設備失效機制的種類繁多，但利用此模式可檢驗及提高電子元件或系統的使用壽命，以達到降低失效率、提升可靠度的目的。

關鍵字

振動 ； 可靠度 ； 疲勞壽命

並列摘要

When electronic devices are subjected to vibration loading for a certain period of time, it is always found the component fatigue failure especially results from resonance. In fact, how long can it last before failure is a problem of interest? In this study, it is aimed to check the electronic component life with a vibration failure test for PBGA components, and combining with finite element analysis(FEA) technique and theoretical calculation to calculate the relating component life.
The experiment is conducted first by taking PBGA components with daisy chain circuit and mounted on a PWB. It is then excited by sinusoidal vibration with the same frequency as the fundamental frequency of component and tested until components failed. The stresses of solder balls itself are always not easily to be acquired from experiment. It is checked with FEA by using the real displacements in vibration test as an input to the model. The resulting stresses of solder balls are then obtained. By combing these stresses and the number of fatigue cycle in vibration test, it is then possible to get the S-N curve of the fatigue life by the curve fitting method. Furthermore, the Weibull’s reliability analysis and Miner’s rule are used to calculate the fatigue life.
The experimental results indicate that the failure cracks are located at the interface between solder balls and PWB. They are fairly close to the findings of the failure locations as often seen in relevant literatures. The procedures as described in the study provide an effective way in verifying the life of the electronic system. The method can be applied to the study of reducing the occurrence of unexpected electronic component failure and also improvement of their reliability in the system design.

並列關鍵字

Vibration ； Reliability ； Fatigue Life ； PBGA ； Daisy Chain ； Weibull

參考文獻

1. Q. J. Yang, H. L. J. Pang, Z. P. Wang, G. H. Lim, F. F. Yap,

and R. M. Lin, “Vibration Reliability Characterization of

PBGA Assembly”, Microelectronics Reliability, Vol. 16, May

“Vibration Reliability Test of PBGA Assembly”, IEEE

Electronics Packaging Technology Conference, 1998